Field of the Invention
Embodiments of the present application relate to the art of a power transmission unit for distributing torque of a drive motor to a right wheel and a left wheel while allowing relative rotation between the right wheel and the left wheel.
Discussion of the Related Art
PCT international Publication WO 2015/008661 describes a drive gear unit having a differential gear unit for distributing output torque of a drive motor to a right wheel and a left wheel, and a concentric motor for controlling a torque distribution ratio to the right wheel and the left wheel. According to the teachings of WO 2015/008661, the differential gear unit comprises two sets of pinion gear units. Sun gears of the pinion gear units are connected to both ends of a rotary shaft, and an input gear to which torque of the drive motor is applied is fitted onto an intermediate portion of the rotary shaft. Internal gears are connected to each other through a reverse rotation member having a pair of shaft members, and a reversing motor is connected to one of the internal gear. Each carrier of the pinion gear units is individually connected to the wheel through a driveshaft.
In the drive gear unit taught by WO 2015/008661, the pinion gear units are disposed on both sides of the input gear, and the internal gears are connected to each other through the reverse rotation member. However, since the reverse rotation member is arranged on an outer side of the input gear, a diameter of the input gear has to be restricted to be smaller than an outer diameter of the internal gear. For this reason, torque of the drive motor delivered to the differential gear unit may not be multiplied sufficiently.